Optical instruments must retain accurate focus throughout a wide range of temperature variations. Unless the instrument is so designed that it is not sensitive to temperature, it is necessary to provide a mechanism for the active compensation of temperature variations.
Known compensation mechanisms are based on connecting the lenses to a platform having a linear motion. Some such mechanisms use stepped linear motors. They have the drawbacks, among others, that they require a large motor and expensive linear supports, have a low rigidity, and require the use of springs to close tolerances. Other such mechanisms have a continuous linear displacement. They comprise a large number of components, require a large motor and springs to close tolerances, and need special solutions to limit the range of motion.
It is a purpose of this invention to provide a mechanism for active thermal compensation, that is free from the drawbacks of prior art mechanisms.
It is another purpose of this invention to provide such a mechanism that is sensitive and precise.
It is a further purpose of this invention to provide such a mechanism that is limited in size and does not require large motors.
It is a still further purpose of this invention to provide such a mechanism that has no tolerance problems.
It is a still further purpose of this invention to provide such a mechanism that has built-in motion limitations.
It is a still further purpose of this invention to provide such a mechanism that provides a self-locking moment, which helps in controlling large and small errors and external random and steady state disturbances.
Other purposes and advantages of the invention will appear as the description proceeds.